Polymerization

ABSTRACT

Polymerization of monofunctional monomers and multifunctional monomers and polymers is initiated by application of electrical field. No solutions containing electrolytes are required. Imagewise field application provides raised polymeric images which may be used for printing plates or lithographic masters.

United States Patent [191 Cressman et a1.

1 1 Apr. 22, 1975 1 1 POLYMERIZATION [75] Inventors: Paul J. Cressman,Fairport; William W. Limburg, Penfield, both of N.Y.; Louis A. Pilato,Bound Brook. NJ.

[73] Assignee: Xerox Corporation, Rochester, NY.

[22] Filed: Apr. 28, 1972 [2]] Appl. No.: 248,770

Related US. Application Data [63] Continuation of Ser. No. 858.062.Sept. 15, 1969,

abandoned.

[52] 11.8. C1 204/165; 204/14 R; 204/23 [51] Int. Cl C07b 29/06 [58]Field of Search 204/180 R, 181 R, 165,

[56] References Cited UNITED STATES PATENTS Miller 204/165 3.155.62911/1964 Tobin et al. 204/168 3,318,790 5/1967 Carbojal et al. 204/1683.321391 5/1967 Warfield et a1. 204/165 3.475.307 10/1969 Knox et al.204/168 FORElGN PATENTS OR APPLlCATlONS 996.018 6/1965 United Kingdom204/165 Primary E.\'aminer F. C. Edmundson Attorney, Agent, or Firm.1ames J. Ralabate; David C. Petre; George J. Cannon [57] ABSTRACTPolymerization of monofunctional monomers and multifunctional monomersand polymers is initiated by application of electrical field. Nosolutions containing electrolytes are required. lmagewise fieldapplication provides raised polymeric images which may be used forprinting plates or lithographic masters.

7 Claims, 2 Drawing Figures PATENTEDAPR22|Q7S 3.879.275

INVENTORS PAUL J. CRESSMAN LOUIS A. PILATO BY WILLIAM W. LIMBURGATTORNEY POLYMERIZATION This is a continuation of application Ser. No.858,062, filed Sept. 15, 1969, now abandoned.

BACKGROUND OF THE INVENTION This invention relates in general topolymerization and in particular to charge injection polymerization.

Addition polymerization of polymerizable unsaturated organic compoundsis accomplished in a variety of ways. The most common method foreffecting the polymerization of unsaturated organic compounds, such asvinyl polymers or vinyl monomers, is to react them chemically in thepresence of a peroxide catalyst at elevated temperatures. Polymerizationis initiated by the thermal decomposition of the peroxide catalyst whichprovides a free radical. Thermal decomposition of an initiator hasdiasdvantages in that heat is required and the rate of generation offree redicals cannot be closely controlled because of the heat capacityof the system.

Another method for effecting the polymerization of unsaturated compoundsis by irradiation. Light of short enough wavelength, i.e., high enoughenergy per quantum can initiate polymerization directly. It iscustomary, however, to use a photochemical initiator to increase therate of polymerization. Radiation induced polymerization hasdisadvantages in that it is much slower than thermally inducedpolymerization and requires high energy light sources, such asultraviolet rays of the type emanating from sunlight or a carbon arclamp.

Another method of polymerizing unsaturated organic compounds is throughthe use of electric discharge in which the monomer is polymerized by thedischarge of electricity through monomer vapors. See, for example, US.Pat. No. 2,632,729 to Woodman. This system, however, requires that themonomer be a vapor at the operating temperature of the system or bevaporized before introduction into the system. High energy electrons arealso used to cross-link polymeric solid materials, such as, polyethyleneor polystyrene. This type of cross-linking, called curing, hasbeneficial effects on the mechanical properties of these polymers.However, this system requires a polymeric solid as a starting materialand very high energy electron sources.

Liquid phase electric field polymerization of unsaturated organiccompounds is also known in the art. For example, acrylonitrile, methylmethacrylate, vinyl ace tate, and styrene can be polymerized by anelectric field. Heretofore, however, the polymerizable materials hadfirst to be dissolved in a solvent such as dimethylforamamide containinga salt such as potassium nitrate or tetramethylammonium perchlorate toconfer conductivity. See, for example, US. Pat. No. 3,193,475 to Baizer.Complex purification techniques are required to recover the product.

SUMMARY OF THE INVENTION it is, therefore, an object of this inventionto provide a system for polymerizing unsaturated organic compounds whichovercomes the above-noted disadvantages.

It is another object of this invention to provide a system forpolymerizing unsaturated organic compounds in an electric field.

It is another object of this invention to provide a system forpolymerizing unsaturated organic compounds which does not require heator thermally decomposed initiators.

It is another object of this invention to provide a system forpolymerizing unsaturated organic compounds in an electric field whichdoes not require vaporization of one or more of the polymerizablematerials.

It is another object of this invention to provide a system forpolymerizing unsaturated organic compounds in the liquid phase in anelectric field which does not require the use of comparativelyconductive media.

It is another object of this invention to provide a system forpolymerizing unsaturated organic compounds which is relatively simpleand does not require relatively complex recovery or purification steps.

It is another object of this invention to provide a system forpolymerizing unsaturated organic compounds in an electric field in imageconfiguration.

It is another object of this invention to provide a system forpolymerizing unsaturated organic compounds in an electric field in imageconfiguration which does not require light sources.

The foregoing objects and others are accomplished in accordance withthis invention by a system comprising placing a liquid polymerizableunsaturated organic compound or mixture of such compounds in anelectroded system. Application of a potential difference across thepolymerizable composition apparently causes a small current to flow intothe polymerizable compound or mixture of such compounds effectingpolymerization. Although the exact mechanism of the polymerizationreaction is not fully understood it is possible that injection ofelectrons into the polymerizable material initiates polymerization.Because a small flow of electrons apparently passes into thepolymerizable mixture, the process is referred to as charge injectionpolymerization. When the desired amount of polymer has been formed,polymerization is stopped by removing the source of the potentialdifference. The electrodes are then separated. The electrode orelectroedes which has the polymer adhering to it may then be flushed toremove any unpolymerized material remaining. The electrode with thepolymer adhering to it may then be used for example as a relief printingplate or lithographic master where the field was applied imagewise. Theprocess may also be used to produce braille type relief images orpolymer sheets or film. The process is also useful for coating metallicmaterials such as wire, nails, and for making printed circuits. One mainadvantage of the present invention for coating over conventional coatingtechniques is that no solvents or electrolytes need be used whichinvariably create pollution problems. To provide imagewisepolymerization one of the electrodes may comprise an insulatingsubstrate having a conductive material on it in image configuration.Here, the image preferably is continuous or electrically connected sothat potential is applied at all parts of the image. Perferably,however, one of the conductive electrodes is masked by an insulatingmaterial in image configuration since a material such as a photo resistmay be used which can be conveniently applied to the electrodes in imageconfiguration.

It should be understood that for the purposes of this disclosure, bypolymerization is meant addition polymerization and is intended also toinclude the crosslinking of polyfunctional polymers and monomers.

Any suitable conductive electrode material may be used. Typicalconductive electrode materials include:

metal surfaces such as aluminum, brass, stainless steel, copper, nickel,zinc, etc., conductively coated glass such as tin or indium oxide coatedglass, aluminum coated glass, similar coatings on plastic substrates orpaper rendered conductive by the inclusion of a suitable chemicaltherein or through conditioning in a humid atmosphere to ensure thepresence therein of sufficient water content to render the materialconductive. NESA (tin oxide coated glass available from the PittsburghPlate Glass Company) electrodes are preferred because being transparentthey allow direct observation of the polymerization.

Where a conductive electrode is to be masked by an insulator in imageconfiguration the insulating masking material may be of any suitablematerial. Typical insulating masking materials include: photoresistcompounds such as those disclosed in U.S. Pat. No. 3,143,423 toReynolds, Van Allan and Borden; and non-photo-polymerized polymers suchas non-selfsupporting or self-supporting films or organic resins,plastics, binders including cellulose, cellulosic materials, andinsulating resins such as lacquer coatings and resin films and layersincluding urea and melaminetype resins and vinyl and acrylic resins andmixtures thereof. The only requirement for the insulative masking isthat it be a significantly better insulator than the electrode on whichit is formed. Photoresist compounds are preferred because of therelative ease with which images may be formed. The processes for placingphoto resist materials on glass, paper or metals in image configurationare known in the art. See, for example, US. Pat. 2,610,120 to Minsk, VanDeusen and Robertson.

Where an insulating substrate is to be overcoated in image configurationwith a conductive material, the conductor may be any suitable material.Typical conductive materials include: copper, aluminum, chro mium andplatinum all of which are commonly vacuum deposited on polymericsubstrates such as those listed below and brass, stainless steel,nickel, zinc and mixtures thereof.

Where an insulating substrate is to be coated in image configurationwith a conductive material the insulating substrate may be of anysuitable material. Typical insulating materials include: glass,phenolics, polyesters, acrylonitrile-butadiene-styrene copolymers,polycarbonates, polyethylene, polypropylene, vinyl, acrylics,polystyrenes, paper, rubber and mixtures thereof.

Any suitable unsaturated organic monomer or polymer or mixtures thereofmay be used. Typical monofunctional monomers include:N-vinylphthalimide, methyl methacrylate, N-vinylcarbazole dissolved infor example acetonitrile or acrylonitrile, N-vinyl pyrrolidone,acrylates such as ethyl acrylate, butyl acrylate, acrylate esters andmixtures thereof. Typical unsaturated multifunctional monomers include:(di), (tri), (tetra), ethylene glycol dimethacrylate, bis (p-methoxybenzal) acetone azine, bis (p-N,N'- dimethylaminobenzylidene) acetone,neopentyl glycol dimethacrylate, hexamethylene-bis-acrylamide, divinylbenzene, allyl methacrylamide, bisphenol A- dimethacrylate,N-N-methylene bisacrylamide, (di), (tri), (tetra), ethylene glycolacrylate, neopentyl glycol diacrylate, bisphenol A-diacrylate,:,Bunsaturated ketones (chalcones) and mixtures thereof.

Typical multifunctional unsaturated polymers include: bis-acrylates andmethacrylates of polyethylene glycols, such as polyethylene glycoldimethacrylate; unsaturated esters of polyols, condensation products of4 (B-hydroxyethoxy)-chalcone with a styrene/maleic anhydride copolymeror other maleic anhydride copolymers and mixtures thereof. Other typicalmultifunctional unsaturated monomers and polymers are disclosed atcolumn 8, line 43, through column 9, line 15 of U.S. Pat. No. 3,060,025to Burg. Muchen and Cohen. A mixture of 7 parts ethylene glycoldimethacrylate (EGDMA) and 3 parts of Atlas 1086 (bisphenolA-epichorohydrin esterified with fumaric acid, available from AtlasChemical Industries, Inc. Wilmington, Del.) is preferred because itpolymerizes readily at a relatively low applied potential. EDGMA is apolymerizable multifunctional monomer, that it, it is a monomer whichhas more than one site of unsaturation and is therefore capable ofrapidly cross-linking the Atlas 1086. Atlas 1086 is a low molecularweight multifunctional polymerizable material which does not requireextensive cross-linking before it forms an insoluble resin with EGDMA.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages of this improved methodof polymerizing unsaturated organic compounds or mixtures of suchcompounds will become apparent upon consideration of the detaileddisclosure of the invention, especially when taken in conjunction withthe accompanying drawings wherein:

FIG. 1 shows a side view of simple exemplary system for carrying out theprocess of this invention wherein a conducting master electrode with aninsulating masking material in image configuration on its surface isused for polymerizing in image configuration.

FIG. 2 shows a side view of a simple exemplary system for carrying outthe process of this invention wherein an insulating master" electrodehaving a conductive masking material in image configuration on itssurface is used for polymerizing in image configuration.

Referring now to FIG. 1, a NESA glass plate 1 having a photoresistmasking material formed on it in image configuration 3 is used as themaster electrode. A Teflon (polytetrafluoroethylene available fromduPont) gasket 4 is placed over the master electrode. The shallow cupformed by the Teflon gasket and master electrode is filled with apolymerizable material 5. A second NESA glass electrode 2 is placed overthe mixture of polymerizable compounds and the Teflon gasket. A source 6of potential difference is then attached to the electrodes: the secondNESA glass electrode 2 is made the negative electrode in the cell. Thepotential is applied until the desired depth of polymer 7 is obtained.Polymer is formed on those areas of the negative electrode directlyopposite the non-masked areas of the conductive master electrode.

Referring now to FIG. 2, a substrate 8 of molded polycarbonate havingaluminum 10 in image configuration, and electrically continuous vacuumdeposited on it is used as the master electrode. Processes for vacuumdepositing metals on plastics are well known. See, for example, ModernPlastics Encyclopedia 1966, page 998. A Teflon gasket 11 is placed overthe master electrode 8. The shallow cup formed by the Teflon gasket andmaster electrode is filled with a polymerizable material 12. An aluminumelectrode 9 is placed over the mixture of polymerizable compounds andthe Teflon gasket. A source 13 of potential difference is then attachedto image and electrode 9. The potential is applied until'the desireddepth of polymer 14 is obtained.

Polymer 114 is formed on those areas of the aluminum electrode 9 whichare directly opposite the conductive image on the master electrode.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples futherspecifically illustrate the present invention. The examples below areintended to illustrate the various preferred embodiments of the improvedpolymerization method. The parts and percentages are by weight unlessotherwise indicated.

EXAMPLE I A 2 inch square by /3 inch thick NESA glass plate is preparedby placing Kodak Photoresist (available from the Eastman Kodak Companyof Rochester, NY.) and described generally as the cinnamate esters ofpolyvinyl alcohol and of cellulose on it in image configuration. Thiselectrode is referred to as the master electrode. A 10 mil thick Teflongasket having a 2 inch square hole is placed over the master electrode.The 10 mil deep "cup formed by the Teflon gasket and the masterelectrode is filled with a polymerizable mixture consisting of about 7parts of ethylene glycol dimethacrylate and about 3 parts of Atlas 1086(bisphenol A- epichlorohydrin esterified with fumaric acid). A second 2inch square by A; inch thick NESA plate is then placed over the Teflongasket and mixture of polymerizable materials. A potential source of1,200 volts do. is connectedto the two electrodes. A higher potentialthan 1,200 volts would result in faster polymerization, however, controlof the extent of polymerization i.e., depth of the polymer on thenegative electrode would not be as accurate, the potential difference islimited by the break-down voltage of the compound or mixture ofcompounds being polymerized. The master electrode is made the positiveelectrode in the cell. Initially, the current flow between the twoelectrodes measures 0.3 milliamperes. This small current flow initiatespolymerization at the surface of the negative electrode. The flow ofcurrent decreases as the polymerization continues. Polymerization iscontinued for 2 minutes. The negative electrode is then removed from thecell and the polymer image bonded to the face of it flushed withacetone. Examination shows a raised polymeric image bonded to thesurface of the NESA plate.

EXAMPLE II A substrate made up of a 2 inch square by inch thick piece ofmolded polycarbonate, made from the phosgenation of bisphenolA(4,4'-dihydroxydiphenyl- 1-1-2-2-pr0pane), is prepared by vacuumdepositing aluminum on its surface in image configuration. The aluminumimage is continuous so that current will flow to all parts of the image.This electrode is referred to as the master electrode. A 10 mil thickTeflon gasket having a 2 inch square hole is placed over the masterelectrode. The 10 mil deep cup formed by the Teflon gasket and masterelectrode is filled with a polymerizable mixture consisting of about 7parts of ethylene glycol dimethacrylate and about 3 parts of Atlas 1086.A 2 inch square by l/l6 inch thick aluminum plate is placed over themixture of polymerizable compounds and the Teflon gasket. A potentialdifference of 1,200 volts do. is applied between the two electrodes. Thealuminum electrode is made the negative electrode in the cell.Application of potential causes a small current to flow into thepolymerizable mixture initiating polymerization at the surface of thealuminum electrode. Polymerization is continued for 2 minutes. Thealuminum electrode is then removed from the cell and the polymer imagebonded to it, flushed with acetone solvent. The aluminum plate with thepolymer image bonded to it may be used as a relief printing plate.

EXAMPLE III A 2 inch square by /8 inch thick NESA glass plate is used asthe master electrode. A 10 mil thick Teflon gasket having a 2 inchsquare hole is placed over the master electrode. The 10 mil deep cupformed by the Teflon gasket and the master electrode is filled with apolymerizable mixture consisting of about 2 parts of divinyl benzene andabout 1 part bis (p-N,N'-dimethylamino benzal) acetone. A 2 inch squareby l/l6 inch thick aluminum electrode is then placed over the Teflongasket and mixture of polymerizable materials. A potential source of1,200 volts is connected to the two electrodes. The master electrode ismade the positive electrode in the cell. The potential is applied for 5minutes. The electrodes are then separated. The polymer may be removedfrom the electrode by scraping lightly with a blade.

EXAMPLE IV A 2 inch square by 4; inch thick NESA glass plate is preparedby placing a photoresist material on it in image configuration. Thiselectrode is referred to as the master electrode. A 10 mil Teflon gaskethaving a 2 inch square hole is placed over the master electrode. The 10mil deep cup formed by the Teflon gasket and the master electrode isfilled with a polymerizable mixture consisting of about 7 parts ofneopentyl glycol dimethacrylate and about 3 parts Atlas 1086 (bisphenolA-epichlorohydrin esterified with fumaric acid). A 2 inch square by l/l6inch thick aluminum plate is then placed over the Teflon gasket andmixture of polymerizable materials. A potential source of 1,200 voltsdo. is connected to the two electrodes. The master electrode is made thepositive electrode in the cell. The potential is applied for 2 minutes.The aluminum electrode is removed from the cell and flushed withacetone. The aluminum electrode with the polymer image bonded to it maybe used as a relief printing plate.

EXAMPLE V 2,4-dicyanobutene-l is polymerized as in Example IV. Thealuminum electrode is removed from the cell and flushed with acetone.The aluminum electrode with the polymer image bonded to it may be usedas a relief printing plate.

EXAMPLE VI (The experiment of Example I is repeated except that a 36 milTeflon spacer is used and 800 volts is applied. The polymerizablecomposition consists of methyl methacrylate. A polymeric relief image isfound adhering to the NESA electrode.

EXAMPLE VII The experiment of Example II is repeated except that a 36mil Teflon spacer is used and 800 volts is applied the polymerizablecomposition consists of methyl methacrylate. A polymeric relief image isfound adhering to the aluminum plate.

EXAMPLE VIII The experiment of Example VI is repeated except that thepolymerizable composition comprises about 1 part of N-vinylcarbazoledissolved in about 4 parts of acrylonitrile. An image is found adheringto the NESA electrode.

Although specific components and proportions have been stated in theabove description of preferred embodiments of the invention, othertypical materials as listed above if suitable may be added to themixture to synergize, enhance or otherwise modify the properties of thepolymer, electrodes and the polymerizable mixture. For example, adiaphragm may be placed between the two electrodes to prevent migrationof polymer to the opposite electrode.

Other modifications and ramifications of the present invention willoccur to those skilled in the art upon a reading of the disclosure.These are intended to be included within the scope of this invention.

What is claimed is:

1. The method of polymerizing comprising the steps of:

a. providing between and in contact with the surface of at least twoelectrodes, a liquid, polymerizable composition comprising unsaturatedvinyl containing compounds capable of undergoing liquid to solidaddition polymerization in response to charge injection from aconductive surface; and

b. in the absence of chemical initiators, catalysts and electrolytes,applying an electrical field across said polymerizable composition untilat least a portion of said polymerizable composition becomes a solid bycharge injection polymerization.

2. The method of claim 1 wherein said polymerizable composition containsmonofunctional monomers.

3. The method of claim 1 wherein said polymerizable composition containsmultifunctional compounds.

4. The method of claim 1 wherein said polymerizable compositioncomprises a mixture of neopentyl glycol dimethacrylate and bisphenolA-epichlorohydrin esterified with fumaric acid.

5. The method of claim 1 wherin said polymerizable composition comprisesa mixture of polyethylene glycol dimethacrylate and bisphenolA-epichlorohydrin esterified with fumaric acid.

6. The method of claim 1 wherein said polymerizable compositioncomprises a mixture of divinyl benzene and bis (p-N,N-dimethylaminobenzylidene) acetone.

7. The method of claim 1 wherein said polymerizable compositioncomprises methyl methacrylate in a solvent.

1. THE METHOD OF POLYMERIZING COMPRISING THE STEPS OF: A. PROVIDINGBETWEEN AND IN CONTACT WITH THE SURFACE OF AT LEAST TWO ELECTRODES, ALIQUID, POLYMERIZABLE COMPOSITION COMPRISING UNSATURATED VINYLCONTAINING COMPOUNDS CAPABLE OF UNDERFORING LIQUID TO SOLID ADDITIONPOLYMERIZA-TION IN RESPONSE TO CHARGE INJECTION FROM A CONDUCTIVESURFACE; AND B. IN THE ABSENCE OF CHEMICAL INITIATORS, CATALYSTS ANDELECTROLYTES, APPLYING AN ELECTRICAL FIELD ACROSS SAID POLYMERIZABLECOMPOSITION UNTIL AT LEAST A PORTION OF SAID POLYMERIZABLE COMPOSITIONBECOMES A SOLID BY CHARGE INJECTION POLYMERIZATION.
 1. The method ofpolymerizing comprising the steps of: a. providing between and incontact with the surface of at least two electrodes, a liquid,polymerizable composition comprising unsaturated vinyl containingcompounds capable of undergoing liquid to solid addition polymerizationin response to charge injection from a conductive surface; and b. in theabsence of chemical initiators, catalysts and electrolytes, applying anelectrical field across said polymerizable composition until at least aportion of said polymerizable composition becomes a solid by chargeinjection polymerization.
 2. The method of claim 1 wherein saidpolymerizable composition contains monofunctional monomers.
 3. Themethod of claim 1 wherein said polymerizable composition containsmultifunctional compounds.
 4. The method of claim 1 wherein saidpolymerizable composition comprises a mixture of neopentyl glycoldimethacrylate and bisphenol A-epichlorohydrin esterified with fumaricacid.
 5. The method of claim 1 wherin said polymerizable compositioncomprises a mixture of polyethylene glycol dimethacrylate and bisphenolA-epichlorohydrin esterified with fumaric acid.
 6. The method of claim 1wherein said polymerizable composition comprises a mixture of divinylbenzene and bis (p-N,N'' -dimethylamino benzylidene) acetone.